'pilaster' originates from Italian, specifically the word 'pilastro', where the root meant 'pillar'.

'pilaster' changed from Late Latin word 'pilastrum' and Italian 'pilastro', and eventually became the modern English word 'pilaster' through use in Renaissance architectural vocabulary.

Initially, it meant 'a small or secondary pillar', but over time it evolved into its current meaning of 'a shallow rectangular column projecting from a wall, mainly decorative'.